A calendar for tree pollen in London

Abstract

Data from a pollcn monitoring n c t w r k in Islington.North 1-ondon, are uscd to construct tree pollen calendars for the trcc seasons lYS7 to 19S9 inclusive.Annual variations in the pollcn abundance and length of flowring scason arc investigatcd for individual spccics in relation to meteorological factors and thc inhcrcnt biological rhythms of trccs.Results indicatc clear relationships bct\vccn scasonal variations in pollcn abundiincc and thc \venthcr.both in thc prcvailing season and also in the precccding year during tlie timc of poiic~i formation.Annual variations cvidcnt in thc pollen records for l?etiiIn and Qiierciis support thc theory of inhcrcnt biennial cycles for thcsc spccics.I'attcrns for other trccs do not sholv clcar trcnds within thc pcriod samplcd.Insufficient information is available to dctcrniinc thc conccntration thrcsliolds of allcrgic rcsponsc for most tree pollcns.but cvidcncc from Finland is uscd to identify the timing and duration of pcriods nhich cxcccd the rcsponsc thresholds for Betitlo.1.